A sample contains two isotopes - one stable and the other unstable. Number of stable nuclei is equal to N s and number of unstable nuclei is equal to N u . After a time the activity of the sample

Question

A sample contains two isotopes - one stable and the other unstable. Number of stable nuclei is equal to $N_{s}$ and number of unstable nuclei is equal to $N_{u}$ . After a time the activity of the sample decreased to one third of the initial activity while the total number of nuclei (excluding decayed nuclei) became half. Find the initial value of the ratio $N_{s} / N_{u}$ .

Answer:

0.33

Solution:

$(N_{S} - \frac{N _{u}}{3}) = \frac{1}{2} {N_{S} + N_{u}}$

$\frac{N _{s}}{2} = \frac{N _{u}}{6}$

$\frac{N _{s}}{N _{u}} = \frac{1}{3}$

TestHub · Accepted Answer

( N S ​ − 3 N u ​ ​ ) = 2 1 ​ { N S ​ + N u ​ } ​ 2 N s ​ ​ = 6 N u ​ ​ ​ ​ N u ​ N s ​ ​ = 3 1 ​

Physics - Modern Physics Question with Solution | TestHub

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